The present invention relates to improvements in apparatus for making composite filter plugs which can be used in the manufacture of filter-tipped cigarettes, cigars or cigarillos.
A composite filter plug comprises two or more fillers which normally consist of different types of filter material and a tubular wrapper which confines the fillers and is open at both ends. As a rule, composite filter plugs are produced in apparatus wherein a continuous rod-like filler consisting of two or more types of alternating filter rod sections is conveyed axially through a wrapping mechanism which drapes the continuous filler into a web of cigarette paper, imitation cork or other suitable wrapping material. The resulting rod is thereupon severed by a suitable cutoff to yield a file of discrete filter plugs each of which comprises at least two rod-like sections consisting of different filter materials, e.g., a first section consisting exclusively of fibrous filamentary filter material and a second section consisting of crepe paper or filamentary filter material interspersed with particles of charcoal.
It is important to insure that the sections which form the continuous filler be disposed end-to-end, i.e., the neighboring sections should abut against each other in order to insure that each of a series of filter plugs will contain two or more different filter rod sections of predetermined length. Since the cutoff invariably severs the rod at regular intervals, the operations which precede the severing of the rod must or should be carried out in such a way that, in the case of relatively simple plugs having two rod-like filter sections of identical length and a tubular wrapper therearound, each and every filter plug of a series will contain two sections each having a length equal to half the length of the plug.
Presently known apparatus cannot produce composite filter plugs with a requisite degree of reproducibility for a variety of reasons. For example, if the speed at which the web travels through the wrapping mechanism deviates only slightly from the speed at which filter rod sections are added to the trailing end of the composite filler, at least some of the sections are caused or allowed to slide with respect to the web. This results in the formation of gaps between neighboring sections. Also, at least some slippage of the web relative to the sections of the composite filler takes place while the web is draped around the filler, primarily because friction between the web and the parts of the wrapping mechanism is different from friction between the sections and the web and/or wrapping mechanism. Still further, the filter rod sections are likely to be displaced by currents of air, especially when the web is transported at a relatively high speed.